Uncovering The Biology Of Cities

The New York Times discusses a growing science subculture — the urban evolutionist. These brave souls are charting the growth of the super-strong mutant rats, fish, bacteria, and bugs that will someday overrun planet:

A small but growing number of field biologists study urban evolution — not the rise and fall of skyscrapers and neighborhoods, but the biological changes that cities bring to the wildlife that inhabits them. For these scientists, New York is one great laboratory.

White-footed mice, stranded on isolated urban islands, are evolving to adapt to urban stress. Fish in the Hudson have evolved to cope with poisons in the water. Native ants find refuge in the median strips on Broadway. And more familiar urban organisms, like bedbugs, rats and bacteria, also mutate and change in response to the pressures of the metropolis.

Pollution has driven some of the starkest examples of evolution around New York. Hudson River fish faced a dangerous threat from PCBs, which General Electric released from 1947 to 1977. PCBs cause deformities in fish larvae. “These are important changes,” said Isaac I. Wirgin of New York University Medical Center. “If you’re missing your jaw, you’re not going to be able to eat.”

Dr. Wirgin and his colleagues were intrigued to discover that the Hudson’s population of tomcod, a bottom-dwelling fish, turned out to be resistant to PCBs. “There was no effect on them at all,” Dr. Wirgin said, “and we wanted to know why.”

Cities attract only a small fraction of evolutionary biologists, who often work in lusher places like the Amazon. But urban evolution is attracting more research these days, because cities are fast-growing, and the urban environment is quickly taking over large areas of the Earth’s surface.

Evolution is not just taking place in New York’s rivers and parks. It’s also taking place inside its hospitals. In 1997, Dr. John Quale, an infectious diseases physician at SUNY Downstate Medical Center, discovered a newly evolved strain of bacteria in the city that is resistant to most antibiotics.

The bacterium, known as Klebsiella pneumoniae, is often found in hospitals, where it can cause pneumonia and other life-threatening infections. Doctors typically treat Klebsiella with a class of antibiotics called carbapenems. Dr. Quale and his colleagues discovered carbapenem-resistant Klebsiella in four hospitals in Brooklyn.